Patent GB-514167-A (GB)
Title: Improvements in or relating to the regulation of electric supply circuits
IPC: H02J7/34
Filed: 1938-04-26
Abstract: 514,167. Automatic control of voltage and current; charging batteries. STANDARD TELEPHONES & CABLES, Ltd., THOMAS, P. R., and KELLY, R. April 26, 1938, No. 12469. [Class 38 (iv)] In a system for the automatic regulation of electric battery charging circuits, a load LC and battery BY in parallel therewith are supplied through a rectifier and a transformer the transformation ratio of which is varied by means of a motor in accordance with 'the voltage across the load or the current flow to the battery. The arrangement is-such that, if the current flow increases beyond a predetermined value, the transformation ratio is reduced irrespective of the value of the voltage across the load circuit, and if the voltage increases beyond a predetermined value the transformation ratio is reduced irrespective of the value of the current flow to the battery. A three-phase supply 1-3 is connected to a transformer VT with a tapped secondary, and through a rectifier R and overload coil OLC to the consuming circuit. The tapping on the secondary is adjustable by a reversible capacitor motor M<1>, M<2> in response to the operation of a voltage relay VC connected across the battery and a current relay CC connected in the position CC<2> in series with the battery. When a switch SW<2> is closed a relay A is operated to close contact a<1> in circuit with a coil NVC which closes switch OLS. The lowest contacts of switch OLS close the circuit of a relay D which operates to close contacts d<2> connected to line wire 2. The relay system ensures that if the voltage across coil VC falls below normal, switch SV<1> closes its left hand contact and relay LR is energized. If the current through coil CC (i.e., CC<2>) is also below normal switch SC1 closes its left hand contact, relay L is energized, closing front contacts lr<3>, l<3> and connecting motor coil M1 to line wire 2. If current through coil CC is normal, the front contacts l<3> remain open and there is no circuit through either coil M1 or M<2>. If, however,' current through coil CC is greater than normal, relay H is energized and line wire 2 is connected over front contacts d<2>, h<4>, d' to coil M<2>, and the motor rotates to reduce the voltage applied to the rectifier. If the voltage be normal and the current low or normal, the circuits between line wire 2 and motor coils M' or M<2> are broken. With a rise in current, the switch SC1 moves to the right, energizing relay H, and the coil M<2> is fed over front contacts d<2>, h<4> and d'. If the voltage be high, switch SV1 moves to the right, and the front contacts hr<4> connect line wire 2 to coil M<2> even if the current in coil CC be normal or low. In the case of each regulating switch, the relay L or LR is disconnected at contacts h1 and hr1 respectively when relay H or HR is energized and the latter are disconnected at l1 and lr1 when relays Land LR respectively are energized. Magnet BR is energized to remove the brake and clutch the shaft driving the contacts of the transformers VT to the motor shaft when relay contacts l<4> and lr<4> or h<5> and hr<5> are closed, the arrangement used preferably being that described in Specification 252,057, [Class 40 (iv)]. Alarm arrangements in case of various failures are provided by a relay F with one side of its winding normally connected to a point connected in star to wires 1, 2, 3. over condensers and fuses, the other side being connected to the neutral wire. Should one phase of the supply fail, relay F, over contacts f1, f2 closes the circuit of a relay B, and over contacts LOC and switch SW<2> to -24V. Relay B operates to close a locking-circuit for itself at b2, and opens contacts b1 to disconnect the battery from relay A which de-energizes, and opens contacts a1, thereby de-energizing coil NVC and opening switch OLS, and also closing contacts a to light a lamp AL to give an alarm. Relay D is also de-energized and connects line wire 2 over closed contacts LOC to coil M2 of the motor. Unless supply line 2 has failed the motor operates the transformer contacts until it is in the minimum output voltage condition, whereupon contacts LOC are opened mechanically by the motor, and the motor circuit is broken.